The proposed Shared Instrumentation Grant would be used to purchase a Philips 410 transmission electron microscope (TEM) for 8 major users at the Eye Research Institute of Retina Foundation. Seven of the major users are established corneal or retinal Principal Investigators whose research routinely requires TEM. The eighth major user is the Institute's Morphology Unit, which provides TEM service for NIH-funded investigators who need electron microscopy occasionally or as a supportive (ancillary) technique. Research projects for which a new TEM would be used include studies of diseased, healing, or normal ocular tissues. Information from such studies has direct rlevance to (1) corneal healing, ulceration, or pathology, (2) glaucoma, (3) diabetic retinopathy, (4) ocular tumors, and (5) normal ocular structure and function. We are requesting funds for a new TEM for the following reasons: (1) ERI has one outdated TEM. (2) Increased demand for TEM time makes it difficult for major users to obtain enough TEM time to assess experiments efficiently. This need has now reached the critical stage. As a result, one major user has had to use a TEM at another institute. With the addition of a new retinal cell biologist (anticipated arrival, Spring 1983), we will be in an impossible situation. TEM time and support will be administered by a committee of major users who will be responsible to the Institute's BRSG committee. Mr. Henry Covington, who currently supervises ERI's old TEM and Scanning EM, will be responsible for maintenance and day-to-day operation of the new TEM.